A material sensing system is used with a vessel to sense the presence of or level of material in the vessel. The system includes a light source/sensor unit. The unit provides light that is directed into a light transmitting probe, one end of which is a sensing point of a lens. When a beam of light reaches the sensing point of the lens, it will either be reflected back to a sensor portion of the unit or transmitted into the surrounding medium. Typically, the beam of light will be reflected when the lens is surrounded by air, and will be transmitted if the lens is surrounded by a material, such as a liquid. When light is reflected back and received by the detector unit, an electrical signal is generated.
Typically, the probe is secured in a housing. In the prior art, the housing includes a case and adaptors that adapt the housing carrying the probe to a vessel. If it is desired to have access to the light source/sensor unit, the probe or other related parts within the housing that require maintenance, the housing must be removed from the vessel to release the probe. U.S. Pat. No. 3,834,235 shows a typical configuration in which a hole is left in the sidewall of the vessel when the source/sensor unit is removed.
What is needed is a probe constructed and arranged with a lens separable from the detector unit to permit the unit to be removed from the vessel without leaving a hole in the sidewall of the vessel. What is also needed is a lens portion of the probe which itself provides the necessary supporting structure to engage and support the light source/sensor unit.